Required Practical 1 - Rate of Enzyme-Controlled Reaction (Colorimter Use)

Question 1

Suggest why a colorimeter is used

Answer 1

• provides quantitative result
• more accurate (not subjective)
• easier to compare

Question 2

Suggest why a water bath is used over a Bunsen burner

Answer 2

• stable temperature
• uniform heating
• safer since no open flame

Question 3

Suggest the importance of calibrating a colorimeter using a control

Answer 3

• consistent readings

- container and buffer solution absorb light as well so provides a base line

Question 4

Suggest why a buffer solution is used in investigations not measuring effect of pH on enzyme activity

Answer 4

• maintains constant pH

- pH is controlled variable

Question 5

Suggest why it is important never to touch the sides of a cuvette

Answer 5

Fingerprints affect the absorbance reading on colorimeter

Question 6

Suggest why a colourless buffer solution should be used in a colorimeter

Answer 6

Coloured buffer solution would affect the absorbance reading on colorimeter

Question 7

Suggest why solutions are mixed gently before placed in a colorimeter

Answer 7

Avoids formation of bubbles or froth which significantly affect absorbance reading on colorimeter

Question 8

Suggest why test tubes are left in the water bath for a period of time before the reaction

Answer 8

• temperature can equilibrate

- reach temperature for reaction to occur

Question 9

Suggest why a water bath at room temperature is used

Answer 9

• keeps test tubes at a constant temperature

- room air temperature fluctuates

Question 10

Describe and explain what you did to make sure the temperatures of the water baths were as reliable as possible

Answer 10

• measure temperature before and after each reaction

- ensure there is little/no change